Manufacturing method for hexafluorocyclobutane

Abstract: Manufacturing method for (Z)-1,2,3,3,4,4-hexafluorocyclobutane which carries out the hydrogen-adding reaction (hydrogen reduction) of the raw material, 1,2-dichlorohexafluorocyclobutane, in the presence of a rhodium catalyst.This method produces a high yield of (Z)-1,2,3,3,4,4-hexafluorocyclobutane.

Description: This invention relates to a method of manufacturing (Z) - 1,2,3,3,4,4-hexafluorocyclobutane, a useful compound that can be employed as an alternate to CFCs and HCFCs presently being used as refrigerants, blowing agents and detergents. Conventional technologies The method for reducing 1,2-dichlorohexafluorocyclobutane using lithium aluminum hydride (LiAlH 4 ), is known as the (Z) - 1,2,3,3,4,4-hexafluorocyclobutane manufacturing method (G. Fuller and J. C. Tatlow, J. Chem Soc., 3198 (1961)). However, the yield of (Z) - 1,2,3,3,4,4-hexafluorocyclobutane using this common method is low as being a 30% yield. The method also produces a large quantity of the geometrical isomer of the target compound, (E) - 1,2,3,3,4,4 - hexafluorocyclobutane, as a by-product. Therefore, this method is not suitable for industrial use. In this paper, (Z) refers to "Zusammen" which corresponds to the "cis" form; and (E) refers to "Entgegen" which corresponds to the "trans" form. Purposes of the invention One purpose of this invention is to provide a high-yield method for manufacturing (Z) - 1,2,3,3,4,4-hexafluorocyclobutane employing the 1,2-dichlorohexafluorocyclobutane reduction reaction. Construction of the invention As a result of thorough study of the manufacturing methods of (Z) - 1,2,3,3,4,4-hexafluorocyclobutane, the inventors have found that the targeted substance can be obtained with a high yield and high selectivity when the hydrogen reduction of the raw material, 1,2-dichlorohexafluorocyclobutane, is carried. out in the presence of a rhodium catalyst. When utilizing this method, (E)- 1,2,3,3,4,4 - hexafluorocyclobutane, the geometrical isomer of the target substance, is not produced. In other words, the essential point of this invention is that it is a method of manufacturing a high yield of (Z) - 1,2,3,3,4,4 - hexafluorocyclobutane by a reaction of adding hydrogen to the raw material, 1,2-dichlorohexafluorocyclobutane; in particular, using hydrogen in an amount of equivalent to double the stoichiometric quantity of the raw material at a temperature of 150 - 300°C in the presence of a rhodium catalyst. Palladium, platinum, rhodium, and Raney nickel, etc., are well-known as catalysts for the hydrogenolysis of halides. When the hydrogen reduction of 1,2-dichlorohexafluorocyclobutane is performed using a palladium catalyst (comparison example 1, below) or a platinum catalyst (comparison example 2, below), not only the raw-material conversion is low, but also (E)-1,2,3,3,4,4 - hexafluorocyclobutane, the geometrical isomer of (Z) - 1,2,3,3,4,4 - hexafluorocyclobutane, is produced and the selectivity decreases. In contrast, using a rhodium catalyst, the raw-material conversion is extremely high, and there is no or a little production of (E) - 1,2,3,3,4,4 - hexafluorocyclobutane, the geometrical isomer of (Z) - 1,2,3,3,4,4-hexafluorocyclobutane. The inventors have clarified that (Z) - 1,2,3,3,4,4 - hexafluorocyclobutane, the target substance, can be obtained with high selectivity. A catalyst carrier can be used that consists of one or more substances selected from common active carbon, alumina, silica and/or zirconia substances. Active carbon is the most desirable and highest target-substance selectivity can be obtained. Either the fixed-bed vapor-phase reaction method or fluidized bed vapor-phase reaction method can be used as a method of vapor-phase reaction. The particle size of the carrier has a few influence on the reaction, although the size of 0.1 - 10 mm is appropriate and desirable. A wide range of supporting concentration from 0.05-10% can be applied, but usually a carrier with a supporting concentration of 0.5 - 5% is recommended. The reaction temperature is normally 150 - 300°C, and the desirable reaction temperature is 175 - 250°C. When the reaction temperature is lower than 150°C, the selectivity is high, but the conversion is low. Moreover, if the reaction temperature exceeds 300°C, large quantities of by-products are produced. In the above-mentioned 1,2-dichlorohexafluorocyclobutane hydrogen reduction reaction, when the quantity of hydrogen is more than the stoichiometric quantity of the raw material, 1,2-dichlorohexafluorocyclobutane, the ratio of hydrogen to the raw material can be drastically changed. However, the hydrogenation is usually carried out using hydrogen in an amount of 2 - 10 times, in particular 2 - 4 times, the stoichiometric quantity. A quantity of hydrogen considerably more than the stoichiometric quantity relative to the total molar quantity of the starting material can be used, for instance 10 mol or more of hydrogen, and the excess hydrogen can be recovered and reused. There is no particular limit for reaction pressure. The reaction can be carried out under pressurized, reduced or normal pressure conditions, although complicated apparatus is needed for the reaction to be carried out under reduced pressure condition. Therefore, it is desirable to carry out the reaction under either pressurized or normal pressure conditions. Contact time is usually 0.1 - 300 seconds, and desirably 1 - 30 seconds. The raw material for the hydrogen reduction reaction, 1,2-dichlorohexafluorocyclobutane, can be synthesized by carrying out a vapor phase dimerization reaction of 1,2,2-trifluoro-1-chloroethylene (chlorotrifluoroethylene) under pressurized conditions, particularly at a pressure of 2 kg/cm 2 or more, in a 200 - 400°C temperature range. When this vapor phase dimerization of chlorotrifluoroethylene is carried out under normal pressure condition, the conversion is low at the reaction temperature of 500°C or less. Moreover, at the reaction temperature of greater than 500°C, a lower range of the selectivity occurs due to the formation of acyclic compounds with 4 carbon atoms, therefore the reaction is not suitable as an industrial manufacturing method. However, when the reaction is carried out under pressurized conditions, 1,2-dichlorohexafluorocyclobutane can be synthesized with good conversion and high selectivity even at a reaction temperature of 400°C or less. Increasing in the pressure for the dimerization reaction the targeted 1,2-dichlorohexafluorocyclobutane can be obtained at a lower temperature with good conversion and high selectivity. When the reaction pressure is increased further, a reaction system durable enough to withstand high pressure is needed. Usually, therefore, it is usually better to carry out this reaction under a pressure of 2-20 kg/cm 2 . In this vapor phase dimerization reaction, decreasing in the flow rate of the raw material, chlorotrifluoroethylene, the conversion rate is increased. However, the conversion can also be increased by using an appropriate packing. Glass beads, nickel beads, globular silica or active carbon can be used as the packing. Industrial feasibility The (Z) - 1,2,3,3,4,4-hexafluorocyclobutane is useful as an alternate for the CFCs and HCFCs used as refrigerants, blowing agents, and detergents. (Z) - 1,2,3,3,4,4 - hexafluorocyclobutane can be manufactured with a high yield by carrying out the hydrogen-adding reaction (hydrogen reduction) using the raw material, 1-2-dichlorohexafluorocyclobutane, in the presence of a rhodium catalyst. Embodiment The invention will be explained in details with reference to the below examples. Actual operation example 1 A reaction tube made of SUS316 with an inner diameter of 7 mm and a length of 150 mm was filled with 1 g of rhodium catalyst supported at 0.5% concentration on active carbon. The reaction tube was heated to 225°C using an electric furnace while a flow of nitrogen gas was passed. After the tube reached the designated temperature, 1,2-dichlorohexafluorocyclobutane was introduced at a flow rate of 1.1 ml/min together with hydrogen at a flow rate of 10.0 ml/min. The reaction temperature was maintained at 225°C. After the produced gas was washed with water, it was analyzed by gas chromatography. Table 1 shows the results. Actual operation example 2 A reaction tube same to that used in actual operation example 1 was filled with 1 g of rhodium catalyst supported at 3% concentration on active carbon. The reaction tube was heated to 225°C using an electric furnace while a flow of nitrogen gas was passed. After the tube reached the designated temperature, 1,2-dichlorohexafluorocyclobutane was introduced at a flow rate of 1.4 ml/min together with hydrogen at a flow rate of 10.0 ml/min. The reaction temperature was maintained at 225°C. After the produced gas was washed with water, it was analyzed by gas chromatography. Table 1 shows the results. Actual operation example 3 A reaction tube same to that used in actual operation example 1 was filled with 1 g of rhodium catalyst supported at 3% concentration on active carbon. The reaction tube was heated to 250°c using an electric furnace while a flow of nitrogen gas was passed. After the tube reached the designated temperature, 1,2-dichlorohexafluorocyclobutane was introduced at a flow rate of 1.5 ml/min together with hydrogen at a flow rate of 10.0 ml/min. The reaction temperature was maintained at 250°C. After the produced gas was washed with water, it was analyzed by gas chromatography. Table 1 shows the results. Actual operation example 4 A reaction tube same to that used in actual operation example 1 was filled with 1 g of rhodium catalyst supported at 3% concentration on active carbon. The reaction tube was heated to 150°C using an electric furnace while a flow of nitrogen gas was passed. After the tube reached the designated temperature, 1,2-dichlorohexafluorocyclobutane was introduced at a flow rate of 1.5 ml/min together with hydrogen at a flow rate of 10.0 ml/min. The reaction temperature was maintained at 150 °C. After the produced gas was washed with water, it was analyzed by gas chromatography. Table 1 shows the results. Comparison example 1 A reaction tube same to that used in actual operation example 1 was filled with 1 g of palladium catalyst supported at 0.5% concentration on active carbon. The reaction tube was heated to 200°C using an electric furnace while a flow of nitrogen gas was passed. After the tube reached the designated temperature, 1,2-dichlorohexafluorocyclobutane was introduced at a flow rate of 1.7 ml/min together with hydrogen at a flow rate of 10.0 ml/min. The reaction temperature was maintained at 200°C. After the produced gas was washed with water, it was analyzed by gas chromatography. Table 1 shows the results. Comparison example 2 A reaction tube same to that used in actual operation example 1 was filled with 1 g of platinum catalyst supported at 0.5% concentration on active carbon. The reaction tube was heated to 150°C using an electric furnace while a flow of nitrogen gas was passed. After the tube reached the designated temperature, 1,2-dichlorohexafluorocyclobutane was introduced at a flow rate of 1.4 ml/min together with hydrogen at a flow rate of 10.0 ml/min. The reaction temperature was maintained at 150°C . After the produced gas was washed with water, it was analyzed by gas chromatography. Table 1 shows the results. Actual operation example Conversion (%) Selectivity (%) Example 1 100 92 Example 2 98 95 Example 3 100 93 Example 4 66 94 Comparison example 1 88 30 Comparison example 2 68 51 We found that by employing the methods based on the invention, the targeted (Z)-1,2,3,3,4,4-hexafluorocyclobutane could be synthesized with good conversion and high selectivity depending on the temperature. Actual operation example 5 A reaction tube made of SUS316 with an inner diameter of 2 cm and a length of 40 cm was filled with 20 ml of glass beads with diameters of approximately 1 mm. Using a back pressure regulating valve, the inner pressure of the tube was regulated at 2 kg/cm 2 . The tube was heated to 300°C using an electric furnace while a flow of nitrogen gas was passed. After the tube reached the designated temperature, chlorotrifluoroethylene was introduced at a flow rate of 18 ml/min. The reaction temperature was maintained at 300°C. After the produced gas was washed with water, it was analyzed by gas chromatography. Table 2 shows the results. Actual operation example 6 A reaction tube same to that used in actual operation example 5 was filled with 20 ml of glass beads with diameters of approximately 1 mm. Using a back pressure regulating valve, the inner pressure of the tube was regulated at 2 kg/cm 2 . The reaction tube was heated to 400°C using an electric furnace while a flow of nitrogen gas was passed. After the tube reached the designated temperature, chlorotrifluoroethylene was introduced at a flow rate of 18 ml/min. The reaction temperature was maintained at 400°C. After the produced gas was washed with water, it was analyzed by gas chromatography. Table 2 shows the results. Actual operation example 7 A reaction tube same to that used in actual operation example 5 was filled with 20 ml of nickel beads with diameters of approximately 2 mm. Using a back pressure regulating valve, the inner pressure of the tube was regulated at 4 kg/cm 2 . The reaction tube was heated to 350°C using an electric furnace while a flow of nitrogen gas was passed. After the tube reached the designated temperature, chlorotrifluoroethylene was introduced at a flow rate of 75 ml/min. The reaction temperature was maintained at 350°C. After the produced gas was washed with water, it was analyzed by gas chromatography. Table 2 shows the results. Actual operation example 8 A reaction tube same to that used in actual operation example 5 was filled with 20 ml of globular silica gel (CARiACT) with an average diameter of approximately 3 mm. Using a back pressure regulating valve, the inner pressure of the tube was regulated at 4 kg/cm 2 . The reaction tube was heated to 350°C using an electric furnace while a flow of nitrogen gas was passed. After the tube reached the designated temperature, chlorotrifluoroethylene was introduced at a flow rate of 75 ml/min. The reaction temperature was maintained at 350°C. After the produced gas was washed with water, it was analyzed by gas chromatography. Table 2 shows the results. Actual operation example Conversion (%) Selectivity (%) Example 5 17 96 Example 6 65 99 Example 7 11 95 Example 8 14 90 From these results, we found that the 1,2-dichlorohexafluorocyclobutane used as the raw material in Examples 1 - 4 can be obtained with high selectivity by carrying out the vapor phase chlorotrifluoroethylene dimerization reaction under pressurized conditions.

Claims: A method of manufacturing (Z)-1,2,3,3,4,4-hexafluorocyclobutane by carrying out vapor-phase hydrogen reduction of 1,2-dichlorohexafluorocyclobutane in the presence of a rhodium catalyst. The manufacturing method described in Claim 1 in which the rhodium catalyst comprises rhodium supported by a carrier consisting of one or more substances selected from active carbon, alumina, silica, and zirconia. The manufacturing method described in Claim 2 in which the carrier support concentration for the rhodium catalyst is set at 0.05 - 10%. The manufacturing method described in one of Claims 1 - 3 in which 2 - 10 equivalents of hydrogen relative to the amount of 1,2-dichlorohexafluorocyclobutane are used. The manufacturing method described in one of Claims 1 - 4 in which the reaction is carried out under a temperature range of 150 - 300°C. The manufacturing method described in one of Claims 1 - 5 in which 1,2-dichlorohexafluorocyclobutane is synthesized by carrying out the vapor-phase 1,1,2-trifluoro-1-chloroethylene dimerization reaction. The manufacturing method described in Claim 6 in which the dimerization reaction is carried out under a pressure range of 1.96 - 19.6 bar (2 - 20 kg/cm 2 ). The manufacturing method described in Claim 6 or 7 in which the dimerization reaction is carried out under a temperature range of 200 - 400°C.

Inventors: AOYAMA HIROKAZU, NAKADA TATSUO, YAMAMOTO AKINORI, AOYAMA, HIROKAZU, NAKADA, TATSUO, YAMAMOTO, AKINORI, NAKADA, TATSUO, YODOGAWA WORKS OF DAIKIN IND. LTD.
Applicants: DAIKIN IND LTD, DAIKIN INDUSTRIES, LIMITED
Application year: 1994
Main classification: C07C23
IPC codes: B01J23